ObjectMapper throws JsonMappingException when it try to construct instance with null field

Question

I try to serializable object to json String, what would have a null fields. When all fields initialize - all works well, but when I set to field null value, I got the exception:

com.fasterxml.jackson.databind.JsonMappingException: (was java.lang.NullPointerException).

My code:

public String toJsonString(T t) throws JsonProcessingException{
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
    String dtoAsString = objectMapper.writeValueAsString(t); //string where I got the exception
    return dtoAsString;
}

Object:

SomeObject{
    @JsonSerialize(using = LocalDateSerializer.class)
    LocalDate date = LocalDate.now();
    Long value = null;
}

PS:

Problem in that what I cannot parse someObject automatically in json, since I got the another exception - I need parse date into special string format. So I need use exactly my way - objectMapper (Gson().toString has wrong serialized my LocalDate value).

Answer 1

I am found the resolving:

Error was occurred since one of the fields has been not initialized, so ObjectMapper trowed exception.

Just add @JsonInclude(JsonInclude.Include.NON_NULL) to you POJO class:

@JsonInclude(JsonInclude.Include.NON_NULL)

SomeObject{
    String date = "11.01.19";
    Long value = null;
}

in result we will be get json without nullable field:

{
    "date" : "11.09.19"
}